What's astonishing though is that this new piece feels like a young man's play. There is an energy, rawness and passion here one doesn't associate with the elegant and witty Stoppard, passages of unbuttoned emotion that go straight to the heart.

It's especially welcome after his last stage outing, that ponderous trilogy 'The Coast of Utopia' about exiled Russian radicals in the 19th century. That had the scent of perspiration and dogged research in the musty stacks of the London Library.

This new piece smells, well, of sex and drugs and rock and roll. It also feels like an exceptionally personal play, for Stoppard appears to be imagining what his life might have been like had he returned to his native Czechoslovakia after the Second World War, rather than beginning a new life in England.

His hero, Jan, is a Czech academic on study leave in Cambridge when the tanks roll into Prague in 1968. He returns home and when his beloved collection of rock records is smashed up by the secret police and his favourite band is imprisoned, he becomes a dissident involved in the Charter 77 movement.

We follow Jan up to the euphoria of the Velvet Revolution in 1990, but we also keep dashing back to Cambridge, where we meet a hardline English Communist professor who stubbornly clings to his faith however severely it is tested. We also meet three generations of his family, with Stoppard exploring family relationships with rare humour, humanity and passion.

And in between scenes, there are glorious bursts of rock music, from the Stones, Pink Floyd, the Velvet Underground and Syd Barrett, the Floyd founder and psychedelic genius who became the great acid casualty of British pop and whose haunting reclusive life in Cambridge becomes a poignant motif of the play.

Rock music thus becomes a symbol of both personal and political freedom and its attendant but exhilarating dangers. Frankly they should gather all the tracks the dramatist has selected and put it out as 'The Best Tom Stoppard Album in the World Ever'.

There are some beautiful speeches from Jan in which he describes his love of England, and its robust tradition of freedom, that surely reflect Stoppard's own feelings for his adopted country. But the play sounds a note of caution. At the end, Jan is warned by a fellow Czech that England is no longer what it was, that "they've put something in the water" and it has become a "democracy of obedience".

One thinks of the present Government, eroding personal liberties with a bland nannyish smile on its face, and reflects that the Czechs fought for a freedom we seem to regard as dispensable. As always in Stoppard there's a feast of ideas - as well as liberty, there are discussions on the poet Sappho and materialist theories of consciousness - but the ideas are constantly accompanied by both strong emotion and excellent jokes.

Trevor Nunn's production could do with a sharper pace and a rougher edge, but there are some tremendous performances, most notably from Rufus Sewell as the endearing, rock-addicted, and remarkably Soppardian Jan, and Sinead Cusack, who plays both a wife and mother dying of cancer, and in the second act, her own ex-hippie daughter with an emotional vulnerability that adds a new dimension to Stoppard's work.

Brian Cox too, is in strong and surprisingly sympathetic form as the old Communist bruiser. I was tempted to end this review by saying It's only rock'n'roll but I like it. In fact, it's about much more than rock'n'roll, and I love it.